4 Answers
4

This can be done from within the Steam client

There is an option within Steam that toggles whether or not Steam starts with your computer. To change it, open up the main Steam window and select 'Settings' from the 'Steam' menu, followed by selecting the 'Interface' tab, which brings up the following screen;

Simply uncheck 'Run Steam when my computer starts' to prevent Steam from starting with your computer. (Obviously if you wanted to Steam to start with your PC, you'd check this box instead of unchecking it!)

In Windows 7 click the Start menu and type msconfig in the Search box. In the System Configuration program that opens, click the Startup tab, and then uncheck Steam. This does pretty much same thing as the Windows 8 tip.